[PATCH] D29103: [tsan] Properly describe GCD worker threads in reports

[Kuba (Brecka) Mracek via Phabricator via llvm-commits]

kubamracek created this revision.
kubamracek added a project: Sanitizers.

When dealing with GCD worker threads, TSan currently prints weird things like "created by thread T-1" and "[failed to restore the stack]" in reports:

  ==================
  WARNING: ThreadSanitizer: data race (pid=18771)
    Write of size 8 at 0x00010ac221a0 by thread T3:
      ...
  
    Previous write of size 8 at 0x00010ac221a0 by thread T1:
      ...
  
    Location is global 'global' at 0x00010ac221a0 (workerthreads.mm.tmp+0x0001000021a0)
  
    Thread T3 (tid=5981759, running) created by thread T-1
      [failed to restore the stack]
  
    Thread T1 (tid=5981757, running) created by thread T-1
      [failed to restore the stack]
  
  SUMMARY: ThreadSanitizer: data race workerthreads.mm:23 in __main_block_invoke_2
  ==================

This patch tries to avoid that and instead print:

  ==================
  WARNING: ThreadSanitizer: data race (pid=18843)
    Write of size 8 at 0x0001044431a0 by thread T3:
      ...
  
    Previous write of size 8 at 0x0001044431a0 by thread T1:
      ...
  
    Location is global 'global' at 0x0001044431a0 (workerthreads.mm.tmp+0x0001000021a0)
  
    Thread T3 (tid=5989400, running) is a GCD worker thread
  
    Thread T1 (tid=5989398, running) is a GCD worker thread
  
  SUMMARY: ThreadSanitizer: data race workerthreads.mm:23 in __main_block_invoke_2
  ==================


Repository:
  rL LLVM

https://reviews.llvm.org/D29103

Files:
  lib/tsan/rtl/tsan_report.cc
  lib/tsan/rtl/tsan_report.h
  test/tsan/Darwin/workerthreads.mm


Index: test/tsan/Darwin/workerthreads.mm
===================================================================
--- test/tsan/Darwin/workerthreads.mm
+++ test/tsan/Darwin/workerthreads.mm
@@ -0,0 +1,43 @@
+// RUN: %clang_tsan %s -o %t -framework Foundation
+// RUN: %deflake %run %t 2>&1 | FileCheck %s
+
+#import <Foundation/Foundation.h>
+
+#import "../test.h"
+
+long global;
+
+int main() {
+  fprintf(stderr, "Hello world.\n");
+  print_address("addr=", 1, &global);
+  barrier_init(&barrier, 2);
+
+  global = 42;
+  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+    global = 43;
+    barrier_wait(&barrier);
+  });
+
+  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+    barrier_wait(&barrier);
+    global = 44;
+
+    dispatch_sync(dispatch_get_main_queue(), ^{
+      CFRunLoopStop(CFRunLoopGetCurrent());
+    });
+  });
+
+  CFRunLoopRun();
+  fprintf(stderr, "Done.\n");
+}
+
+// CHECK: Hello world.
+// CHECK: WARNING: ThreadSanitizer: data race
+// CHECK: Write of size 8
+// CHECK: Previous write of size 8
+// CHECK: Location is global
+// CHECK: Thread {{.*}} is a GCD worker thread
+// CHECK-NOT: failed to restore the stack
+// CHECK: Thread {{.*}} is a GCD worker thread
+// CHECK-NOT: failed to restore the stack
+// CHECK: Done.
Index: lib/tsan/rtl/tsan_report.h
===================================================================
--- lib/tsan/rtl/tsan_report.h
+++ lib/tsan/rtl/tsan_report.h
@@ -90,7 +90,7 @@
   uptr os_id;
   bool running;
   char *name;
-  int parent_tid;
+  u32 parent_tid;
   ReportStack *stack;
 };
 
Index: lib/tsan/rtl/tsan_report.cc
===================================================================
--- lib/tsan/rtl/tsan_report.cc
+++ lib/tsan/rtl/tsan_report.cc
@@ -235,9 +235,15 @@
   if (rt->name && rt->name[0] != '\0')
     Printf(" '%s'", rt->name);
   char thrbuf[kThreadBufSize];
-  Printf(" (tid=%zu, %s) created by %s",
-    rt->os_id, rt->running ? "running" : "finished",
-    thread_name(thrbuf, rt->parent_tid));
+  const char *thread_status = rt->running ? "running" : "finished";
+  if (rt->parent_tid == kInvalidTid) {
+    Printf(" (tid=%zu, %s) is a GCD worker thread\n", rt->os_id, thread_status);
+    Printf("\n");
+    Printf("%s", d.EndThreadDescription());
+    return;
+  }
+  Printf(" (tid=%zu, %s) created by %s", rt->os_id, thread_status,
+         thread_name(thrbuf, rt->parent_tid));
   if (rt->stack)
     Printf(" at:");
   Printf("\n");


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